Technical Field
The present invention relates to processing for recognizing a character by image processing, and particularly relates to a technique for cutting out each character as a recognition target, from an image as a processing target.
Related Art
In character recognition processing, generally, characters are individually cut out from a gray-scale image generated by capturing an image of a character string. Then, matching processing (model matching) using various character models is performed on each character thus cut out, and thus the content of the character string is recognized. In processing for cutting out a character, binary data or gray-scale data of an image as the processing target is projected in x and y axis directions, and a portion corresponding to the character is extracted from a projected pattern generated for each axis. Thus, an area (hereinafter, referred to as “character area”) corresponding to each character is specified.
As a prior art related to character recognition processing, Patent Literature 1 describes a technique, in which, from a gray level histogram obtained by the projection processing, the width of the cut out character is compared with the threshold. When the character width is larger than a threshold, it is determined that a plurality of characters might be in contract with each other, and thus cutting out is performed again (see paragraphs 0024 to 0027, and the like). Furthermore, the cutting out processing is performed again also when the reliability of a recognition processing result after the cutting out is low, or when an image as a matching target matches a model showing a part of a character (the left-hand side of a Kanji character and the like) (see paragraph 0037 and the like).
Patent Literature 2 describes a technique of calculating a matching reliability level by performing provisional matching processing after a character is cut out. A standard character length of a full-size character is determined based on a character candidate satisfying a condition such as having the matching reliability level not lower than a reference value. Half-size character cutting out processing based on the standard character length is performed on an area having the matching reliability level lower than a predetermined level (see paragraphs 0061 and 0078 to 0085, and the like).
PTL 1: Japanese Unexamined Patent Application Publication No. 1997-282417
PTL 2: Japanese Unexamined Patent Application Publication No. 2010-44485